(706765) 2010 TK7
{{Short description|Near-Earth asteroid and Earth trojan}}
{{Use dmy dates|date=January 2022}}
{{DISPLAYTITLE:{{mp|(706765) 2010 TK|7}}}}
{{Infobox planet
| minorplanet = yes
| name = {{mp|(706765) 2010 TK|7 ² }}
| background = #FFC2E0
| image = PIA14405-full crop.jpg
| image_scale =
| caption = {{longitem|Asteroid {{mp|2010 TK|7}} (circled in green) in image from the WISE spacecraft|style=padding: 4px; line-height: 1.4em;}}
| discovered = 1 October 2010
| discoverer = WISE spacecraft
| discovery_site = LEO, polar orbit
| mpc_name = {{mp|2010 TK|7}}
| alt_names =
| pronounced =
| named_after =
| mp_category = {{Ubl
| Aten (2014)
| Apollo (2013)[https://web.archive.org/web/20130328180427/http://www.minorplanetcenter.net/db_search/show_object?object_id=2010%20TK7-#560953 WayBack Machine 2013 Epoch@MPC]
}}
| epoch = 13 January 2016 (JD 2457400.5)
| uncertainty = 0
| observation_arc = 768 days (2.10 yr)
| semimajor = {{Convert|0.99972|AU|Gm|abbr=on}}
| perihelion = {{Convert|0.80918|AU|Gm|abbr=on}}
| aphelion = {{Convert|1.1903|AU|Gm|abbr=on|lk=on}}
| eccentricity = 0.19059
| inclination = [20.890°<
| asc_node = [96.498°^
| arg_peri = [45.927°^
| mean_anomaly = 354.14°
| avg_speed = 29.8 km/s{{efn|name=speed|1={{nowrap|1=v = 42.1219 {{radic|1/0.9989 − 0.5/0.9989}}}}.}}
| mean_diameter = {{val|379|123|u=m}}
| albedo = {{val|0.059|0.049}}
| density =
| surface_grav =
| magnitude = 20.8 (when ~\near Earth) to 23.6
| abs_magnitude = 20.8
| mean_motion = {{Deg2DMS|0.98602|sup=ms}} / day
| moid = {{Convert|0.0837911|AU|Gm|abbr=on}}
}}
{{mp|(706765) 2010 TK|7}} (provisional designation {{mp|2010 TK|7}}) is a sub-kilometer Near-Earth asteroid and the first Earth trojan discovered; it precedes Earth in its orbit around the Sun. anonmas objects are most easily conceived as orbiting at a Lagrangian point, a dynamically stable location (where the combined gravitational force acts through the Sun's and Earth's barycenter) 60 degrees ahead of or behind a massive orbiting body, in a type of 1:1 orbital resonance. In reality, they oscillate around such a point. Such objects had previously been observed in the orbits of Mars, Jupiter, Neptune, and the Saturnian moons Tethys and Dione.
{{mp|2010 TK|7}} has a diameter of about {{convert|300|m|-2|sp=us}}. Its path oscillates about the Sun–Earth {{L4}} Lagrangian point (60 degrees ahead of Earth), shuttling between its closest approach to Earth and its closest approach to the {{L3}} point (180 degrees from Earth).
The asteroid was discovered in October 2010 by the NEOWISE team of astronomers using NASA's Wide-field Infrared Survey Explorer (WISE).
Discovery
WISE, a space telescope launched into Earth orbit in December 2009, imaged {{mp|2010 TK|7}} in October 2010 while carrying out a program to scan the entire sky from January 2010 to February 2011. Spotting an asteroid sharing Earth's orbit is normally difficult from the ground, because their potential locations are generally in the daytime sky. After follow-up work at the University of Hawaii and the Canada–France–Hawaii Telescope, its orbit was evaluated on 21 May 2011 and the trojan character of its motion was published in July 2011. The orbital information was published in the journal Nature by Paul Wiegert of the University of Western Ontario, Martin Connors of Athabasca University and Christian Veillet, the executive director of the Canada–France–Hawaii Telescope.
Physical and orbital characteristics
{{mp|2010 TK| ² 7}} has an absolute magnitude of luminosity (determinable because of its known location) of about 20.8. Based on an assumed albedo of 0.1, its estimated diameter is about 300 meters. No spectral data are yet available to shed light on its composition. {{mp|2010 TK|7}} would exert a surface gravitational force of less than {{frac|1|20,000}} that of Earth.
At the time of discovery, the asteroid orbited the Sun with a period of 365.389 days, close to Earth's 365.256 days. As long as it remains in 1:1 resonance with Earth, its average period over long time intervals will exactly equal that of Earth. On its eccentric (e = 0.191) orbit, {{mp|2010 TK|7}}'s distance from the Sun varies annually from 0.81 AU to 1.19 AU. It orbits in a plane inclined about 21 degrees to the plane of the ecliptic.
Trojans do not orbit right at Lagrangian points but oscillate in tadpole-shaped loops around them (as viewed in a corotating reference frame in which the planet and Lagrangian points are stationary); {{mp|2010 TK|7}} traverses its loop over a period of 395 years.{{refn|group=lower-alpha|Because of its orbital inclination and eccentricity, {{mp|2010 TK|7}}'s position relative to Earth is actually a complicated, tightly coiled spiral; however, if its average position relative to Earth over a year is represented by a single point, that point will follow the tadpole loop.}} {{mp|2010 TK|7}}'s loop is so elongated that it sometimes travels nearly to the opposite side of the Sun with respect to Earth. Its movements do not bring it any closer to Earth than 20 million kilometers (12.4 million miles), which is more than 50 times the distance to the Moon. {{mp|2010 TK|7}} was at the near-Earth end of its tadpole in 2010–2011, which facilitated its discovery.
{{mp|2010 TK|7}}'s orbit has a chaotic character, making long-range predictions difficult. Prior to 500 AD, it may have been oscillating about the {{L5|nolink=yes}} Lagrangian point (60 degrees behind Earth), before jumping to {{L4|nolink=yes}} via {{L3|nolink=yes}}. Short-term unstable libration about {{L3|nolink=yes}}, and transitions to horseshoe orbits are also possible. Newer calculations based on an improved orbit determination confirm these results.
{{multiple image | align = center| direction = horizontal | width = 300
| header = Animation of {{mp|2010 TK|7}} orbit from 1600 to 2500
| image1 = Animation of 2010 TK7.gif
| caption1 = Relative to Sun and Earth
| image2 = Animation of 2010 TK7 around Earth.gif
| caption2 = Around Earth
| image3 = Animation of 2010 TK7 around Sun.gif
| caption3 = Around Sun
| footer ={{legend2| Yellow|Sun}}{{·}}{{legend2| RoyalBlue|Earth}}{{·}}{{legend2|Magenta|{{mp|2010 TK|7}} }}
}}
{{clear}}
Accessibility from Earth
File:2010TK7 Viwe form plar coordinates.png
File:Lagrange points2.svg plot showing Earth's Lagrangian points (not to scale); contours around {{L4|nolink=yes}} and {{L5|nolink=yes}} represent tadpole loop paths]]
Because Earth trojans share Earth's orbit and have little gravity of their own, less energy might be needed to reach them than the Moon, even though they are much more distant. However, {{mp|2010 TK|7}} is not an energetically attractive target for a space mission because of its orbital inclination: It moves so far above and below Earth's orbit that the required change in velocity for a spacecraft to match its trajectory coming from Earth's would be 9.4 km/s, whereas some other near-Earth asteroids require less than 4 km/s.
During the 5 December 2012 Earth close approach of {{convert|0.197|AU|km mi|abbr=on|lk=on}}, the asteroid had an apparent magnitude of about 21.
{{clear}}
See also
- {{mpl|614689|2020 XL|5}}, the second Earth trojan discovered
- Claimed moons of Earth
- Provisional designation in astronomy, the naming convention used for astronomical objects immediately following their discovery
Notes
{{notelist|1}}
References
{{reflist|2
|refs=
|type=2012-11-07 last obs
|title=JPL Small-Body Database Browser: 2010 TK7
|url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=3548081
|access-date=31 March 2016}}
|title=2010 TK7 Orbit
|publisher=Minor Planet Center
|url=http://www.minorplanetcenter.net/db_search/show_object?object_id=2010+TK7
|access-date=1 September 2015}}
|last1=Choi |first1=Charles Q.
|title=First Asteroid Companion of Earth Discovered at Last
|url= http://www.space.com/12443-earth-asteroid-companion-discovered-2010-tk7.html
|date=27 July 2011
|publisher=Space.com
|access-date=2011-07-27}}
|last1=Connors |first1=Martin
|last2=Wiegert |first2=Paul
|last3=Veillet |first3=Christian
|title=Earth's Trojan asteroid
|date=27 July 2011
|journal=Nature
|volume=475 |issue=7357 |pages=481–483
|doi=10.1038/nature10233
|bibcode = 2011Natur.475..481C
|pmid=21796207|s2cid=205225571
}}
|url=http://www.nasa.gov/mission_pages/WISE/news/wise20110727.html
|title=NASA's WISE Mission Finds First Trojan Asteroid Sharing Earth's Orbit
|date=27 July 2011
|work=NASA
|access-date=1 September 2015
|archive-date=2 May 2017
|archive-url=https://web.archive.org/web/20170502055548/https://www.nasa.gov/mission_pages/WISE/news/wise20110727.html
|url-status=dead
}}
|last=Keys
|first=Sonia
|title=MPEC 2010-T45 : 2010 TK7
|publisher=IAU Minor Planet Center
|date=2010-10-07
|url=http://www.minorplanetcenter.net/mpec/K10/K10T45.html
|access-date=2011-07-31}}
|url=http://www.astro.uwo.ca/~wiegert/2010TK7/
|title=Earth's first Trojan asteroid: 2010 TK7
|work=Astro.uwo.ca
|date=27 July 2011
|access-date=1 September 2015}}
|url=http://www.nbcnews.com/id/43914196
|archive-url=https://web.archive.org/web/20200924000821/http://www.nbcnews.com/id/43914196
|url-status=dead
|archive-date=24 September 2020
|title=Found at last: First Earth companion asteroid
|work=NBC News
|date=27 July 2011
|access-date=28 July 2011
}}
|type=2011-08-03 last obs (arc=40 days; Uncertainty=2)
|title=JPL Close-Approach Data: (2010 TK7)
|url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2010TK7;cad=1#cad
|access-date=2012-01-21}}
|title=AstDyS 2010TK7 Ephemerides for 2012
|publisher=Department of Mathematics, University of Pisa, Italy
|url=https://newton.spacedys.com/astdys/index.php?pc=1.1.3.1&n=2010TK7&oc=500&y0=2012&m0=11&d0=01&h0=0&mi0=0&y1=2013&m1=1&d1=1&h1=0&mi1=0&ti=1.0&tiu=days
|access-date=2012-01-21}}
|first1 = Carlos |last1 = de la Fuente Marcos
|first2 = Raúl |last2 = de la Fuente Marcos
|date = 18 February 2021
|title = Transient Terrestrial Trojans: Comparative Short-term Dynamical Evolution of 2010 TK7 and 2020 XL5
|journal = Research Notes of the American Astronomical Society
|volume = 5
|issue = 2
|pages = 29
|bibcode = 2021RNAAS...5...29D
|doi = 10.3847/2515-5172/abe6ad
|doi-access= free
}}
}}
- {{cite news|url=https://www.bbc.co.uk/news/science-environment-14307987|title=Trojan asteroid seen in Earth's orbit by Wise telescope|publisher= BBC News|date=2011-07-28|access-date=2011-07-29|first=Jonathan |last= Amos}}
External links
- [http://www.minorplanetcenter.net/db_search/show_object?object_id=2010+TK7&commit=Show MPC Database entry for {{mp|2010 TK|7}}]
- [https://web.archive.org/web/20110805084918/http://www.nasa.gov/multimedia/videogallery/index.html?media_id=103550791 NASA animation of its motion]
- [http://www.nasa.gov/mission_pages/WISE/news/wise20110727vid.html Alternate NASA animation of {{mp|2010 TK|7}} motion] {{Webarchive|url=https://web.archive.org/web/20130302070109/http://www.nasa.gov/mission_pages/WISE/news/wise20110727vid.html |date=2 March 2013 }}
- {{NeoDys|2010+TK7}}
- {{ESA-SSA|2010TK7}}
- {{JPL small body}}
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